Image sensor and method of fabricating the same

ABSTRACT

An image sensor includes a substrate, a shallow trench isolation layer, a first deep trench isolation layer, and a second deep trench isolation layer. The substrate includes a first surface, a second surface opposing the first surface, and a plurality of unit pixel regions. The shallow trench isolation layer is adjacent to the first surface. The first deep trench isolation layer is adjacent to the shallow trench isolation layer and extends toward the second surface in the substrate. The second deep trench isolation layer is adjacent to the second surface and vertically overlaps the first deep trench isolation layer. The first and second deep trench isolation layers isolate the unit pixel regions from each other.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2014-0076512, filed on Jun. 23, 2014,and entitled, “Image Sensor and Method of Fabricating the Same,” isincorporated by reference herein in its entirety.

BACKGROUND

1. Field

One or more embodiments described herein relate to an image sensor and amethod of fabricating an image sensor.

2. Description of the Related Art

An image sensor is a semiconductor device that coverts optical imagesinto electrical signals. An image sensor may be categorized as a chargecoupled device (CCD)-type or a complementary metal-oxide-semiconductor(CMOS)-type. A CMOS image sensor (CIS) may include pixels arranged in atwo-dimensional pattern. Each pixel may include a photodiode thatconverts incident light into an electrical signal.

Since their inception, the integration of image sensors has beensteadily increasing. This increase in integration has resulted in asmaller pixel size, which may adversely affect reliability andperformance. For example, the smaller pixel size may allow cross-talk tooccur between adjacent pixels.

SUMMARY

In accordance with one embodiment, an image sensor includes a substrateincluding a first surface, a second surface opposing the first surface,and a plurality of unit pixel regions; a shallow trench isolation layeradjacent to the first surface; a first deep trench isolation layeradjacent to the shallow trench isolation layer and extending toward thesecond surface in the substrate; and a second deep trench isolationlayer adjacent to the second surface and vertically overlapping thefirst deep trench isolation layer. The first and second deep trenchisolation layers may isolate the unit pixel regions from each other.

The first deep trench isolation layer may be in contact with the seconddeep trench isolation layer. The first deep trench isolation layer mayinclude a filling insulation layer; and a poly-silicon pattern in thefilling insulation layer. The poly-silicon pattern may be doped withN-type dopants.

The image sensor may include a dopant injection region in the substrateand along sidewalls of the first and second deep trench isolationlayers. The second deep trench isolation layer may include a fixedcharge layer; and a filling insulation layer in the fixed charge layer.The second deep trench isolation layer may include an oxygen permeationpreventing layer between the fixed charge layer and the fillinginsulation layer. The fixed charge layer may overlap the second surface.

The second deep trench isolation layer may include a gap-fillsupplementary layer between the oxygen permeation preventing layer andthe filling insulation layer. A sidewall of the second deep trenchisolation layer may be horizontally spaced apart from a sidewall of thefirst deep trench isolation layer.

The first deep trench isolation layer may be vertically spaced apartfrom the second deep trench isolation layer. The image sensor furtherincludes a channel stop region between the first deep trench isolationlayer and the second deep trench isolation layer. At least one of thefirst and second deep trench isolation layers may include an air gapregion. The image sensor may include a fixed charge layer on the secondsurface.

The deep trench isolation region may surround each of the unit pixelregions when viewed from a plan view. A width of the first deep trenchisolation layer may be different from a width of the second deep trenchisolation layer. A vertical length of the first deep trench isolationlayer may be different from a vertical length of the second deep trenchisolation layer. A vertical length of each of the first and second deeptrench isolation layers may be in a range of 2 μm to 5 μm.

At least one of the shallow trench isolation layer, the first deeptrench isolation layer, or the second deep trench isolation layer mayhave an inclined sidewall. A width of the shallow trench isolation layermay progressively increase towards the first surface. A width of thefirst deep trench isolation layer may progressively increase towards thefirst surface. A width of the second deep trench isolation layer mayprogressively increase towards the second surface.

In accordance with another embodiment, an image sensor includes asubstrate including a first surface, a second surface opposing the firstsurface, and a plurality of unit pixel regions; a first deep trenchisolation layer adjacent to the first surface and extending toward thesecond surface in the substrate; and a second deep trench isolationlayer adjacent to the second surface. The second deep trench isolationlayer overlaps the first deep trench isolation layer when viewed from aplan view. The first and second deep trench isolation layers isolate theunit pixel regions from each other. The first deep trench isolationlayer may have substantially a T-shaped cross section.

In accordance with another embodiment, an image sensor includes a firstpixel region; a second pixel region; a fixed charge layer over the firstand second pixel regions, a first isolation layer between the first andsecond pixel regions; and a second isolation layer between the first andsecond pixel regions, wherein the second isolation layer overlaps thefirst isolation layer and wherein the first and second isolation layersisolate the first pixel region from the second pixel region.

The fixed charge layer may include a material to induce accumulation ofholes adjacent a surface of each of the first and second pixel regions.The image sensor may include a poly-silicon pattern in the secondisolation layer. The poly-silicon pattern may have a first thermalexpansion coefficient, the first and second pixel regions may be in alayer having a second thermal expansion coefficient, and the firstthermal expansion coefficient may be substantially equal to the secondthermal expansion coefficient.

The second isolation layer may includes at least one of an oxygenpermeation preventing layer or a filling insulation layer. The secondisolation layer may include a first layer; and a second layer on thefirst layer, wherein the first layer is closer to the first isolationlayer than the second layer, and wherein the second layer is closer to asurface to receive incident light than the first layer. The first layermay include one or more materials, and the second layer may include oneor more materials different from the one or more materials of the firstlayer.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describingin detail exemplary embodiments with reference to the attached drawingsin which:

FIG. 1 illustrates an embodiment of an image sensor;

FIG. 2 illustrates a portion of a layout of an image sensor according toone embodiment;

FIG. 3 illustrates a view along section line A-A′ in FIG. 2;

FIGS. 4 to 11 illustrate stages in an embodiment of a method forfabricating an image sensor in FIG. 3;

FIGS. 12A to 12E illustrate modified embodiments of the image sensor inFIG. 3;

FIG. 13 illustrates another embodiment of an image sensor;

FIG. 14 illustrates a stage in an embodiment of a method for fabricatingthe image sensor of FIG. 13;

FIG. 15 illustrates another embodiment of an image sensor;

FIG. 16 illustrates another embodiment of an image sensor;

FIG. 17 illustrates a stage in an embodiment of a method for fabricatingthe image sensor of FIG. 16;

FIG. 18 illustrates another embodiment of an image sensor;

FIG. 19 illustrates another embodiment of an image sensor:

FIG. 20 illustrates a stage in an embodiment of a method for fabricatingthe image sensor of FIG. 19;

FIG. 21 illustrates another embodiment of an image sensor;

FIG. 22 illustrates another embodiment of an image sensor;

FIG. 23 illustrates an embodiment of an electronic device; and

FIGS. 24 to 28 illustrate embodiments of multimedia devices.

DETAILED DESCRIPTION

Example embodiments are described more fully hereinafter with referenceto the accompanying drawings; however, they may be embodied in differentforms and should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully conveyexemplary implementations to those skilled in the art.

In the drawings, the dimensions of layers and regions may be exaggeratedfor clarity of illustration. It will also be understood that when alayer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “under” another layer, it canbe directly under, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

Although corresponding plan views and/or perspective views of somecross-sectional view(s) may not be shown, the cross-sectional view(s) ofdevice structures illustrated herein provide support for a plurality ofdevice structures that extend along two different directions as would beillustrated in a plan view, and/or in three different directions aswould be illustrated in a perspective view. The two different directionsmay or may not be orthogonal to each other. The three differentdirections may include a third direction that may be orthogonal to thetwo different directions. The plurality of device structures may beintegrated in a same electronic device. For example, when a devicestructure (e.g., a memory cell structure or a transistor structure) isillustrated in a cross-sectional view, an electronic device may includea plurality of the device structures (e.g., memory cell structures ortransistor structures), as would be illustrated by a plan view of theelectronic device. The plurality of device structures may be arranged inan array and/or in a two-dimensional pattern.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit the invention. As usedherein, the singular terms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. It will beunderstood that when an element is referred to as being “connected” or“coupled” to another element, it may be directly connected or coupled tothe other element or intervening elements may be present.

Similarly, it will be understood that when an element such as a layer,region or substrate is referred to as being “on” another element, it canbe directly on the other element or intervening elements may be present.In contrast, the term “directly” means that there are no interveningelements. It will be further understood that the terms “comprises”,“comprising,”, “includes” and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Additionally, the embodiment in the detailed description will bedescribed with sectional views as ideal exemplary views of the presentembodiments. Accordingly, shapes of the exemplary views may be modifiedaccording to manufacturing techniques and/or allowable errors.Therefore, the embodiments of the present embodiments are not limited tothe specific shape illustrated in the exemplary views, but may includeother shapes that may be created according to manufacturing processes.Areas exemplified in the drawings have general properties, and are usedto illustrate specific shapes of elements. Thus, this should not beconstrued as limited to the scope of the present embodiments.

It will be also understood that although the terms first, second, thirdetc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another element. Thus, a first element insome embodiments could be termed a second element in other embodimentswithout departing from the teachings of the present invention. Exemplaryembodiments of aspects of the present embodiments explained andillustrated herein include their complementary counterparts. The samereference numerals or the same reference designators denote the sameelements throughout the specification.

Moreover, exemplary embodiments are described herein with reference tocross-sectional illustrations and/or plane illustrations that areidealized exemplary illustrations. Accordingly, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, exemplaryembodiments should not be construed as limited to the shapes of regionsillustrated herein but are to include deviations in shapes that result,for example, from manufacturing. For example, an etching regionillustrated as a rectangle will, typically, have rounded or curvedfeatures. Thus, the regions illustrated in the figures are schematic innature and their shapes are not intended to illustrate the actual shapeof a region of a device and are not intended to limit the scope ofexample embodiments.

As appreciated by the present inventive entity, devices and methods offorming devices according to various embodiments described herein may beembodied in microelectronic devices such as integrated circuits, whereina plurality of devices according to various embodiments described hereinare integrated in the same microelectronic device. Accordingly, thecross-sectional view(s) illustrated herein may be replicated in twodifferent directions, which need not be orthogonal, in themicroelectronic device. Thus, a plan view of the microelectronic devicethat embodies devices according to various embodiments described hereinmay include a plurality of the devices in an array and/or in atwo-dimensional pattern that is based on the functionality of themicroelectronic device.

The devices according to various embodiments described herein may beinterspersed among other devices depending on the functionality of themicroelectronic device. Moreover, microelectronic devices according tovarious embodiments described herein may be replicated in a thirddirection that may be orthogonal to the two different directions, toprovide three-dimensional integrated circuits.

Accordingly, the cross-sectional view(s) illustrated herein providesupport for a plurality of devices according to various embodimentsdescribed herein that extend along two different directions in a planview and/or in three different directions in a perspective view. Forexample, when a single active region is illustrated in a cross-sectionalview of a device/structure, the device/structure may include a pluralityof active regions and transistor structures (or memory cell structures,gate structures, etc., as appropriate to the case) thereon, as would beillustrated by a plan view of the device/structure.

FIG. 1 illustrates an embodiment of an image sensor which includes aplurality of pixels. Each pixel includes a photoelectric conversionregion PD, a transfer transistor TX, a source follower transistor SX, areset transistor RX, and a selection transistor AX.

The transfer transistor TX, the source follower transistor SX, the resettransistor RX, and the selection transistor AX may respectively includea transfer gate TG, a source follower gate SF, a reset gate RG, and aselection gate SEL. A photoelectric converter is provided in thephotoelectric conversion region PD. The photoelectric converter may beor include a photodiode that includes, for example, an N-type dopantregion and a P-type dopant region. A drain of the transfer transistor TXmay be a floating diffusion region FD. The floating diffusion region FDmay also be a source of the reset transistor RX. The floating diffusionregion FD may be electrically connected to the source follower gate SFof the source follower transistor SX. The source follower transistor SXis connected to the selection transistor AX. The reset transistor RX,the source follower transistor SX, and the selection transistor AX maybe shared by pixels adjacent to each other, so the integration densityof the image sensor may be improved.

Operation of the image sensor will now be described with reference toFIG. 1. First, in a dark state, a power voltage VDD may be applied to adrain of the recess transistor RX and a drain of the source followertransistor SX to discharge charges remaining in the floating diffusionregion FD. Thereafter, if the reset transistor RX is turned-off andlight is input from the outside into the photoelectric conversion regionPD, electron-hole pairs may be generated in the photoelectric conversionregion PD. Holes are moved into and accumulated in the P-type dopantregion, and electrons are moved into and accumulated in the N-typedopant region.

The transfer transistor TX may be turned-on to transfer the charges intothe floating diffusion region FD. The transferred charges may beaccumulated in the floating diffusion region FD. A gate bias of thesource follower transistor SX may be changed in proportion to the amountof the accumulated charges, to cause variation in the source potentialof the source follower transistor SX. At this time, if the selectiontransistor AX is turned-on, a signal caused by the charges may be sensedthrough a column line.

FIG. 2 illustrates an example layout of an image sensor, and FIG. 3 is across-sectional view taken along line A-A′ in FIG. 2. Referring to FIGS.2 and 3, the example layout includes a substrate 3 having unit pixelregions UP. The substrate 3 may be or include a silicon wafer, asilicon-on-insulator (SOI) substrate, or a semiconductor epitaxiallayer. The substrate 3 may include a first surface 3 a and a secondsurface 3 b that are opposite to each other. Light may be incident onthe second surface 3 b, and one or more integrated circuits may be onthe first surface 3 a.

A shallow trench isolation layer 9 may be on the first surface 3 a todefine active regions AR. The shallow trench isolation layer 9 may be ina shallow trench 53. The unit pixel regions UP may be isolated from eachother by a deep trench isolation region 20. The deep trench isolationregion 20 may extend from the shallow trench isolation layer 9 to thesecond surface 3 b in a third direction Z.

The deep trench isolation region 20 may have a mesh shape when viewedfrom a plan view. For example, the deep trench isolation region 20 maysurround each of the unit pixel regions UP. Since the image sensoraccording to the present embodiment includes the deep trench isolationregion 20 separating the unit pixel regions UP from each other,cross-talk between pixels adjacent to each other may be reduced orprevented.

A first dopant injection region 41 may be disposed in the substrate 3 ofeach of the unit pixel regions UP separated by the deep trench isolationregion 20. The first dopant injection region 41 may be adjacent to thesecond surface 3 b. A second dopant injection region 43 may be under thefirst dopant injection region 41. The second dopant injection region 43may be adjacent to the first surface 3 a. The second dopant injectionregion 43 may be doped with dopants having a conductivity type oppositeto the dopants of the first dopant injection region 41. For example, thefirst dopant injection region 41 may be doped with N-type dopants, andthe second dopant injection region 43 may be doped with P-type dopants.The first dopant injection region 41 and the second dopant injectionregion 43 may constitute the photoelectric conversion region PD of FIG.1.

The shallow trench isolation layer 9 may be on the first surface 3 a todefine the active region AR in the unit pixel region UP. A floatingdiffusion region FD may be in the active region AR and may be adjacentto the first surface 3 a. A transfer gate TG may be disposed on thefirst surface 3 a to cross the active region AR, e.g., to partiallyoverlap the floating diffusion region. As illustrated in FIG. 3, thetransfer gate TG may be a vertical-type transfer gate shape thatincludes a portion extending in the third direction Z into the substrate3. Alternatively, the transfer gate TG may be a flat-type transfer gatethat is on only the first surface 3 a of the substrate 3.

A transistor 15 may be at a position spaced apart from the transfer gateTG. The transistor 15 may correspond to at least one of the sourcefollower transistor SX, the reset transistor RX, or the selectiontransistor AX. A multi-layered interlayer insulating layer 17 andinterconnections 19 may be on the first surface 3 a. The interlayerinsulating layer 17 may be covered with a first passivation layer 21.

The deep trench isolation region 20 may include a first deep trenchisolation layer 7 adjacent to the shallow trench isolation layer 9 and asecond deep trench isolation layer 11 adjacent to the second surface 3b. The first deep trench isolation layer 7 is disposed in a first deeptrench 51, and the second deep trench isolation layer 11 is disposed ina second deep trench 55. In the present embodiment, the first and seconddeep trench isolation layers 7 and 11 may include, for example, siliconoxide. A top surface of the second deep trench isolation layer 11 may becoplanar with the second surface 3 b.

In the present embodiment, the first deep trench isolation layer 7 mayhave a first vertical length or thickness D1 (e.g., in the thirddirection Z) and the second deep trench isolation layer 11 may have asecond vertical length or thickness D2 (e.g., in the third direction Z).The first vertical length D1 may be equal to or different from thesecond vertical length D2. In some embodiments, the first deep trenchisolation layer 7 and the second deep trench isolation layer 11 may havethe same width W1, as illustrated in FIG. 3. In addition, a sidewall ofthe first deep trench isolation layer 7 may be aligned a sidewall of thesecond deep trench isolation layer 11, as illustrated in FIG. 3. Each ofthe first and second vertical lengths D1 and D2 of the first and seconddeep trench isolation layers 7 and 11 may be in a predetermined range.An example of the predetermined range is 2 μm to 5 μm. The predeterminedrange may be different in another embodiment.

A fixed charge layer 23 is on the second surface 3 b. The fixed chargelayer 23 may include, for example, a metal oxide layer including oxygenhaving a content ratio lower than its stoichiometric ratio, or a metalfluoride layer including fluorine having a content ratio lower than itsstoichiometric ratio. Thus, in one embodiment, the fixed charge layer 23may have negative fixed charges. The fixed charge layer 23 may include ametal oxide or metal fluoride that includes at least one of hafnium(Hf), zirconium (Zr), aluminum (Al), tantalum (Ta), titanium (Ti),yttrium (Y), tungsten (W), or lanthanoid. In one example embodiment, thefixed charge layer 23 may include a hafnium oxide layer or an aluminumfluoride layer. Holes may be accumulated in the neighborhood of thesecond surface 3 b by the fixed charge layer 23. Thus, it is possible toeffectively reduce occurrence of a dark current and/or white spots.

The fixed charge layer 23 may be covered with a second passivation layer27. Each of the first and second passivation layers 21 and 27 mayinclude at least one of a silicon nitride layer or a polyimide layer. Acolor filter 29 and a micro-lens 31 may be sequentially stacked on thesecond passivation layer 27 in each of the unit pixel regions UP. Thecolor filters 29 may be arranged in a matrix, or other predeterminedpattern, form to form a color filter array. The color filter array mayhave, for example, a Bayer pattern including a red filter, a greenfilter, and a blue filter. In other embodiments, the color filter arraymay include a different combination of color filters, e.g., a yellowfilter, a magenta filter, and a cyan filter. In addition, the colorfilter array may include a white filter.

FIGS. 4 to 11 are cross-sectional views illustrating stages in oneembodiment of a method for fabricating the image sensor in FIG. 3.Referring to FIG. 4, the substrate 3 including the plurality of unitpixel regions UP is prepared. The substrate 3 includes the first surface3 a and the second surface 3 b opposite to each other. The substrate 3may be or include, for example, a semiconductor wafer (e.g., a siliconwafer or a silicon-on-insulator (SOI) substrate) or a semiconductorepitaxial layer.

Referring to FIG. 5, a plurality of ion implantation processes may beperformed to form a first dopant injection region 41 and a second dopantinjection region 43 in the substrate 3 of each of the unit pixel regionsUP. For example, the first dopant injection region 41 may be doped withN-type dopants, and the second dopant injection region 43 may be dopedwith P-type dopants. A first mask pattern M1 that defines a first deeptrench 51 may be formed on the substrate 3. The substrate 3 may bepatterned using the first mask pattern M1 as an etch mask to form thefirst deep trench 51 in the substrate 3. The first deep trench 51 isformed at a boundary between the unit pixel regions UP. A bottom surfaceof the first deep trench 51 is spaced apart from the second surface 3 bof the substrate 3. The first deep trench 51 may be formed to have afirst depth D3 and a first width W1, e.g., a thickness in the firstdirection X.

Referring to FIG. 6, the first mask pattern M1 is removed. An insulatinglayer such as a silicon oxide layer may be formed on the first surface 3a. A planarization etching process may be performed on the insulatinglayer to form the first deep trench isolation layer 7 in the first deeptrench 51.

Referring to FIG. 7, a portion of the substrate 3 and a portion of thefirst deep trench isolation layer 7 that are adjacent to the firstsurface 3 a may be removed to form a shallow trench 53. An insulatinglayer such as a silicon oxide layer may be formed on the first surface 3a, and a planarization etching process may be performed on theinsulating layer to form a shallow trench isolation layer 9 in theshallow trench 53. Thus, the first deep trench isolation layer 7 mayhave the first vertical length D1.

Referring to FIG. 8, a transfer gate TG, a floating diffusion region FD,and a transistor 15 may be formed to be adjacent to the first surface 3a. Thereafter, the interconnections 19, the interlayer insulating layer17, and the first passivation layer 21 may be formed.

Referring to FIG. 9, the substrate 3 may be overturned (e.g., rotated180°) so the second surface 3 b faces upward. A planarization etchingprocess may be performed to remove a portion of the substrate 3 by afirst thickness Ti. At this time, the first deep trench isolation layer7 may not be exposed.

Referring to FIG. 10, a second mask pattern M2 may be formed on thesecond surface 3 b of the substrate 3. The second mask pattern M2 mayhave an opening that overlaps with the first deep trench isolation layer7 when viewed from a plan view. The substrate 3 may be etched using thesecond mask pattern M2 as an etch mask to form the second deep trench 55exposing the first deep trench isolation layer 7. At this time, thesecond deep trench 55 may have a second depth D4 and a second width W2.The second depth D4 may be equal to or different from the first depthD3. In the embodiment of FIG. 10, the second width W2 is substantiallyequal to the first width W1.

Referring to FIG. 11, the second mask pattern M2 is removed. Aninsulating layer such as a silicon oxide layer may be formed on thesecond surface 3 b. A planarization etching process may be performed onthe insulating layer to form a second deep trench isolation layer 11 inthe second deep trench 55.

Referring again to FIG. 3, subsequently, a fixed charge layer 23 isdeposited on the second surface 3 b of the substrate 3. The fixed chargelayer 23 may be formed, for example, by a chemical vapor deposition(CVD) method or an atomic layer deposition (ALD) method. The fixedcharge layer 23 may include, for example, a metal oxide layer includingoxygen having a content ratio lower than its stoichiometric ratio, or ametal fluoride layer including fluorine having a content ratio lowerthan its stoichiometric ratio. The fixed charge layer 23 may include ametal oxide or metal fluoride including at least one selected from agroup consisting of hafnium (Hf), zirconium (Zr), aluminum (Al),tantalum (Ta), titanium (Ti), yttrium (Y), tungsten (W), or lanthanoid.

In some embodiments, process temperatures of subsequent processes, to beperformed after the formation of the fixed charge layer 23, may be equalto or lower than that of the process of forming the fixed charge layer23. Thus, the content ratio of the oxygen, which is lower than itsstoichiometric ratio, may be maintained in the fixed charge layer 23. Asa result, in one embodiment, the fixed charge layer 23 may have negativefixed charges. A second passivation layer 27 may be formed on the secondsurface 3 b of the substrate. Thereafter, the color filter 29 and themicro-lens 31 may be sequentially formed on each of the unit pixelregions UP.

In the present embodiment, a plurality of deep trenches may be formedfor the formation of the deep trench isolation region 20. For example,to form the deep trench isolation region 20, the first surface 3 a ofthe substrate 3 may be etched to form the first deep trenches 51 of thefirst depth D3, and the second surface 3 b of the substrate 3 may beetched to form the second deep trenches 55 of the second depth D4. Thus,an etched depth during one etching process may be reduced to improve amargin of the etching process.

In addition, the depths, which are to be filled with insulating layers,of the first and second deep trenches 51 and 55 may be reduced toimprove gap-fill characteristics of the first and second deep trenchisolation layers 7 and 11. Thus, reproducibility of reliable imagesensors may increase.

Moreover, if a trench is formed by one etching process for the formationof the deep trench isolation portion, the trench may be very deep. Thus,the width of an upper portion of the trench may be sufficiently large toprevent a not-open phenomenon of the trench. As a result, it may bedifficult to reduce the size of the deep trench isolation portion. Forexample, it may be difficult to realize a highly integrated image sensorunder some circumstances. However, since the deep trench isolationregion 20 is formed using two etching processes in the presentembodiment, the width of the deep trench isolation region 20 may berelatively reduced. As a result, a highly integrated image sensor may beeasily realized.

FIGS. 12A to 12E are cross-sectional views illustrating various modifiedembodiments of the image sensor of FIG. 3. Referring to FIG. 12A, asidewall of the first deep trench isolation layer 7 may be spaced apartfrom a sidewall of the second deep trench isolation layer 11 in an imagesensor according to this modified embodiment. Misalignment of the secondmask pattern M2 may occur when the second deep trench 55 is formed asdescribed with reference to FIG. 10, so the image sensor according tothis modified embodiment may be fabricated.

The second deep trench 55 may partially expose the top surface of thefirst deep trench isolation layer 7 by the misalignment of the secondmask pattern M2. The second deep trench isolation layer 11 filling thesecond deep trench 55 may cover a portion of the top surface and aportion of the sidewall of the first deep trench isolation layer 7.Other elements and/or other fabricating processes of the image sensoraccording to this modified embodiment may be the same as or similar tocorresponding elements and corresponding fabricating processes of theimage sensor described with reference to FIGS. 3 to 11.

Referring to FIG. 12B, the width W1 of the first deep trench isolationlayer 7 may be different from the width W2 of the second deep trenchisolation layer 11. In this modified embodiment, the width W1 of thefirst deep trench isolation layer 7 may be greater than the width W2 ofthe second deep trench isolation layer 11. Also, the vertical length D1of the first deep trench isolation layer 7 may be different from thevertical length D2 of the second deep trench isolation layer 11. Otherelements and/or other fabricating processes of the image sensoraccording to this modified embodiment may be the same as or similar tocorresponding elements and corresponding fabricating processes of theimage sensor described with reference to FIGS. 3 to 11.

Referring to FIG. 12C, the width W1 of the first deep trench isolationlayer 7 may be different from a width W2 of the second deep trenchisolation layer 11. In this modified embodiment, the width W1 of thefirst deep trench isolation layer 7 may be less than the width W2 of thesecond deep trench isolation layer 11. Other elements and/or otherfabricating processes of the image sensor according to the presentmodified embodiment may be the same as or similar to correspondingelements and corresponding fabricating processes of the image sensordescribed with reference to FIG. 12B.

Referring to FIG. 12D, a sidewall of the shallow trench isolation layer9 may be inclined in an image sensor according to this modifiedembodiment. The width of the shallow trench isolation layer 9 may becomeprogressively greater toward the first surface 3 a, or may becomeprogressively less toward the second surface 3 b. A sidewall of thefirst deep trench isolation layer 7 may also be inclined. The width ofthe first deep trench isolation layer 7 may become progressively greatertoward the first surface 3 a, or may become progressively less towardthe second surface 3 b. A sidewall of the second deep trench isolationlayer 11 may also be inclined. A width of the second deep trenchisolation layer 11 may become progressively less toward the firstsurface 3 a, or may become progressively greater toward the secondsurface 3 b. Thus, a central portion of the deep trench isolation region20 may be relatively narrow, and the deep trench isolation region 20 maybecome progressively wider toward its bottom and top ends.

In this modified embodiment, one surface of the shallow trench isolationlayer 9, which is disposed between the sidewall of the shallow trenchisolation layer 9 and the sidewall of the first deep trench isolationlayer 7 adjacent thereto, may be flat and in contact with the substrate3. For example, a lower corner of the first deep trench isolation layer7 may contact the one surface of the shallow trench isolation layer 9and may be spaced apart from an upper corner of the shallow trenchisolation layer 9.

A sidewall of the shallow trench 53 may be inclined, so the shallowtrench isolation layer 9 may be formed to have an inclined sidewall.Likewise, a sidewall of the first deep trench 51 may be inclined, so thefirst deep trench isolation layer 7 may be formed to have an inclinedsidewall. A sidewall of the second deep trench 55 may be inclined, sothe second deep trench isolation layer 11 may have an inclined sidewall.

Also, a gradient of the sidewall of the shallow trench isolation layer9, a gradient of the sidewall of the first deep trench isolation layer7, and a gradient of the sidewall of the second trench isolation layer11 may be equal to or different from each other. Other elements and/orother fabricating processes of the image sensor according to the presentmodified embodiment may be the same as or similar to correspondingelements and corresponding fabricating processes of the image sensordescribed with reference to FIGS. 3 to 11.

Referring to FIG. 12E, sidewalls of the shallow, first deep, and seconddeep trench isolation layers 9, 7, and 11 may be inclined in an imagesensor according to this modified embodiment. A lower corner of thefirst deep trench isolation layer 7 may contact an upper corner of theshallow trench isolation layer 9. Also, gradient of the sidewall of theshallow trench isolation layer 9, a gradient of the sidewall of thefirst deep trench isolation layer 7, and a gradient of the sidewall ofthe second trench isolation layer 11 may be equal to or different fromeach other. Other elements and/or other fabricating processes of theimage sensor according to the present modified embodiment may be thesame as or similar to corresponding elements and correspondingfabricating processes of the image sensor described with reference toFIG. 12D.

FIG. 13 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 13, in the image sensor of thisembodiment, a first deep trench isolation layer 7 may include a firstfilling insulation layer 7 a and a poly-silicon pattern 7 b. The firstfilling insulation layer 7 a may conformally cover a sidewall and abottom surface of the first deep trench 51. The poly-silicon pattern 7 bmay fill the first deep trench 51. The poly-silicon pattern 7 b may bedoped with N-type dopants. The first filling insulation layer 7 a mayinclude a silicon oxide-based material. Since a thermal expansioncoefficient of the poly-silicon pattern 7 b is approximately equal tothat of silicon of the substrate 3, it is possible to reduce a physicalstress caused by a difference between thermal expansion coefficients ofmaterials of the an image sensor.

A second deep trench isolation layer 11 may include a fixed charge layer23, an oxygen permeation preventing layer 24, a gap-fill supplementarylayer 25, and a second filling insulation layer 26 which aresequentially and conformally formed on a sidewall and a bottom surfaceof the second deep trench 55. The fixed charge layer 23 may be the sameas or similar to the fixed charge layer 23 described with reference toFIG. 3. The second filling insulation layer 26 may include a siliconoxide-based material. The oxygen permeation preventing layer 24 mayinclude, for example, a silicon nitride-based material. The oxygenpermeation preventing layer 24 may prevent oxygen from being supplied tothe fixed charge layer 23 when the second filling insulation layer 26 isformed.

Since the fixed charge layer 23 may include an oxygen-poor metal oxide,it may have negative fixed charges. If the oxygen permeation preventinglayer 24 does not exist, oxygen may be combined with the metal oxide ofthe fixed charge layer 23 during the formation of the second fillinginsulation layer 26. Thus, the fixed charge layer 23 may lose thefunction having the negative fixed charges. The gap-fill supplementarylayer 25 may include, for example, a hafnium oxide layer. The gap-fillsupplementary layer 25 may improve a gap-fill characteristic of thesecond filling insulation layer 26.

The fixed charge layer 23, the oxygen permeation preventing layer 24,the gap-fill supplementary layer 25, and the second filling insulationlayer 26 which constitute the second deep trench isolation layer 11 mayextend onto the second surface 3 b. In the present embodiment, since thefixed charge layer 23 surrounds a top surface and a sidewall of thefirst dopant injection region 41, the dark current characteristic may beimproved more significantly. Other elements of the image sensoraccording to the present embodiment may be the same as or similar tocorresponding elements of the image sensor described with reference toFIG. 3.

FIG. 14 is a cross-sectional view illustrating a stage in an embodimentof a method for fabricating the image sensor of FIG. 13. Referring toFIG. 14, a first filling insulation layer 7 a may be conformally formedand a poly-silicon layer may be formed to fill the first trench 51 whenthe first deep trench isolation layer 7 is formed in FIG. 6, e.g.,before the substrate is rotated. Thereafter, a planarization etchingprocess may be performed on the first filling insulation layer 7 a andthe poly-silicon layer to leave the first filling insulation layer 7 aand a poly-silicon pattern 7 b in the first deep trench 51.

When the shallow trench 53 is formed, the first filling insulation layer7 a and the poly-silicon pattern 7 b may also be etched. A shallowtrench isolation layer 53 may be formed in the shallow trench 53. Theprocesses described with reference to FIGS. 8 and 9 may be performed,and, then, a second mask pattern M2 may be formed on the second surface3 b. The substrate 3 may be etched using the second mask pattern M2 asan etch mask to form a second deep trench 55 exposing the first deeptrench isolation layer 7. At this time, a top surface of the firstfilling insulation layer 7 a may be exposed.

Referring again to FIG. 13, the fixed charge layer 23, the oxygenpermeation preventing layer 24, the gap-fill supplementary layer 25, andthe second filling insulation layer 26 may be sequentially andconformally formed to form the second deep trench isolation layer 11filling the second deep trench 55. The second passivation layer 27, thecolor filter 29, and the micro-lens 31 may be sequentially formed on thesecond filling insulation layer 26. Other fabricating processes of thepresent embodiment may be the same as or similar to correspondingprocesses of the embodiment described with reference to FIGS. 4 to 11.

FIG. 15 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 15, in the image sensor according tothis embodiment, a third dopant injection region 30 may be disposed inthe substrate 3 adjacent to the sidewalls of the first and second deeptrenches 51 and 55. The third dopant injection region 30 may extendalong the sidewalls of the first and second deep trenches 51 and 55. Thethird dopant injection region 30 may be doped with dopants have aconductivity type that is the same as that of the dopants included inthe second dopant injection region 43. For example, the third dopantinjection region 30 may be doped with P-type dopants. The dopantconcentration of the third dopant injection region 30 may be higher thanthat of the second dopant injection region 43. Other elements of theimage sensor according to this embodiment may be the same as or similarto corresponding elements of the image sensor described with referenceto FIG. 13.

In a method for fabricating the image sensor according to the presentembodiment, a tilt ion implantation process may be performed after eachof the first and second deep trenches 51 and 55 is formed, therebyforming the third dopant injection region 30. Other fabricatingprocesses of the present embodiment may be the same as or similar tocorresponding processes of the embodiment described with reference toFIG. 14.

FIG. 16 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 16, in the image sensor according tothis embodiment, a deep trench isolation region 20 may include a firstdeep trench isolation layer 7, a second deep trench isolation layer 11,and a channel stop region 12 disposed between the first and second deeptrench isolation layers 7 and 11. The first deep trench isolation layer7 is spaced apart from the second deep trench isolation layer 11. Thechannel stop region 12 may be doped with dopants having a conductivitytype that is the same as that of the dopants included in the seconddopant injection region 43. For example, the channel stop region 12 maybe doped with P-type dopants. The dopant concentration of the channelstop region 12 may be higher than that of the second dopant injectionregion 43. Other elements of the image sensor according to the presentembodiment may be the same as or similar to corresponding elements ofthe image sensor described with reference to FIG. 3.

FIG. 17 is a cross-sectional view illustrating a stage in an embodimentof a method for fabricating the image sensor of FIG. 16. Referring toFIG. 17, an ion implantation process may be performed to form a channelstop region 12 under a bottom surface of the first deep trench 51 afterthe first deep trench 51 is formed in FIG. 5. The ion implantationprocess may be performed in a third direction Z substantiallyperpendicular to the first surface 3 a of the substrate 3. The processesdescribed with reference to FIGS. 6 to 9 may be performed, and, then, asecond deep trench 55 may be formed. At this time, the second deeptrench 55 may be spaced apart from the first deep trench isolation layer7 and may expose the channel stop region 12. Subsequent processes to beperformed thereafter may be the same as or similar to the processesdescribed with reference to FIG. 11.

FIG. 18 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 18, in this embodiment, a deep trenchisolation region 20 may penetrate the substrate 3 so as to be connectedto the first surface 3 a and the second surface 3 b. For example, a topsurface of a first deep trench isolation layer 7 may be coplanar withthe first surface 3 a. Other elements of the image sensor according tothe present embodiment may be the same as or similar to correspondingelements of the image sensor described with reference to FIG. 3.

The order of the formation of the shallow trench isolation layer 9 andthe first deep trench isolation layer 7 may be changed to fabricate theimage sensor of FIG. 18. For example, the shallow trench isolation layer9 may be first formed through the first surface 3 a. Next, the shallowtrench isolation layer 9 disposed at the boundary of the unit pixelregions UP and the substrate 3 may be successively etched to form afirst deep trench 51. Thereafter, the first deep trench isolation layer7 may be formed to fill the first deep trench 51. Other fabricatingprocesses of the present embodiment may be the same as or similar tocorresponding processes of the embodiment described with reference toFIGS. 4 to 11.

FIG. 19 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 19, in the present embodiment, a shallowtrench isolation layer disposed at the boundary of the unit pixelregions UP and a first deep trench isolation layer 7 c may constituteone united body. Thus, the first deep trench isolation layer 7 c mayhave a T-shaped cross section. A deep trench isolation region 20 maypenetrate the substrate 3 so as to be connected to the first surface 3 aand the second surface 3 b. A shallow trench isolation layer 7 d, thatis spaced apart from the first deep trench isolation layer 7 c, may havethe same shape as the shallow trench isolation layer 9 illustrated inFIG. 3. Other elements of the image sensor according to the presentembodiment may be the same as or similar to corresponding elements ofthe image sensor described with reference to FIG. 3.

FIG. 20 is a cross-sectional view illustrating a stage in an embodimentof a method for fabricating the image sensor of FIG. 19. Referring toFIG. 20, shallow trenches 53 defining active regions AR may be formed inthe substrate 3 through the first surface 3 a. Thereafter, a third maskpattern M3 defining a first deep trench 51 may be formed on the firstsurface 3 a. The third mask pattern M3 may partially fill the shallowtrenches 53. The substrate 3 may be etched using the third mask patternM3 as an etch mask to form a first deep trench 51 under a bottom surfaceof the shallow trench 53 disposed at the boundary of the unit pixelregions UP. Subsequently, the third mask pattern M3 is removed. Thus,the shallow trenches 53 and the first deep trench 51 are formed.

The first deep trench 51 and the shallow trench 53 adjacent thereto mayform a dual damascene hole shape. An insulating layer may be formed tofill the shallow trenches 53 and the first deep trench 51. Aplanarization etching process may be performed on the insulating layerto form the shallow trench isolation layer 7 d and the first deep trenchisolation layer 7 c, which are illustrated in FIG. 19. Other processesof the present embodiment may be the same as or similar to correspondingprocesses of the embodiment described with reference to FIGS. 4 to 11.

FIG. 21 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 21, in this embodiment, a deep trenchisolation region 20 may include a first deep trench isolation layer 7 cadjacent to the first surface 3 a, a second deep trench isolation layer11 adjacent to the second surface 3 b, and a channel stop region 12disposed between the first and second deep trench isolation layers 7 cand 11. The first deep trench isolation layer 7 c may be the same as orsimilar to the first deep trench isolation layer described withreference to FIG. 19. The channel stop region 12 may be the same as orsimilar to the channel stop region 12 described with reference to FIG.16.

FIG. 22 is a cross-sectional view illustrating another embodiment of animage sensor. Referring to FIG. 22, in this embodiment, a first deeptrench isolation layer 7 may include a first filling insulation layer 7a and a first air gap region AG1 formed within the first fillinginsulation layer 7 a. A second deep trench isolation layer 11 mayinclude a fixed charged layer 23, a second filling insulation layer 26,and a second air gap region AG2 formed within the second fillinginsulation layer 26. At this time, the second filling insulation layer26 may include a silicon nitride-based material to prevent the functionof the fixed charge layer 23 from being deteriorated.

FIG. 23 illustrates an embodiment of an electronic device which mayinclude an image sensor in accordance with one or more of theaforementioned embodiments. The electronic device may be a digitalcamera, a mobile device, or another electronic system or apparatus.

Referring to FIG. 23, the electronic device includes an image sensor100, a processor 230, a memory device 300, a display device 410, and adata bus 500. As illustrated in FIG. 23, the image sensor 100 maycapture external image information in response to one or more controlsignals of the processor 230. The processor 230 may store the capturedimage information in the memory device 300 through the data bus 500. Theprocessor 230 may output the image information stored in the memorydevice 300 through the display device 410.

FIGS. 24 to 28 illustrate various embodiments of multimedia devices,each of which may include one or more of the aforementioned embodimentsof an image sensor. The image sensor may be applied, for example, tovarious multimedia devices having an image photographing function. Forexample, the image sensor may be applied to a mobile or smart phone 2000as illustrated in FIG. 24 and/or a tablet or smart tablet 3000 asillustrated in FIG. 25.

In addition, the image sensor may be applied to a notebook computer 4000as illustrated in FIG. 26 and/or a television or smart television 5000as illustrated in FIG. 27. Moreover, the image sensor may be applied toa digital camera or digital camcorder 6000 as illustrated in FIG. 28.

In accordance with one or more of the aforementioned embodiments, animage sensor includes the deep trench isolation portion which isolatesunit pixel regions from each other, in order to reduce or eliminatecross-talk between adjacent pixels. In addition, the image sensor mayinclude a fixed charge layer, which, for example, may have negativefixed charges. Thus, the holes may be accumulated in the neighborhood ofthe fixed charge layer. As a result, it is possible to effectivelyreduce the occurrence of dark current and white spots.

In these or other embodiments, a poly-silicon pattern may be disposed inthe deep trench isolation layer. The thermal expansion coefficient ofthe poly-silicon pattern may be approximately equal to that of siliconof the substrate. As a result, it is possible to reduce physical stresscaused by a difference between thermal expansion coefficients ofmaterials in the image sensor.

In accordance with these or other embodiments, a method for fabricatingan image sensor includes forming a first deep trench by etching a firstsurface of a substrate, and a second deep trench by etching a secondsurface of the substrate. For example, a plurality of the etchingprocesses may be performed to form the deep trench isolation portion.Thus, etched depths of the etching processes may be reduced in order toimprove margins of the etching processes. In addition, the depths of thefirst and second deep trenches may be reduced to improve the gap-fillcharacteristics of the first and second deep trench isolation layers. Asa result, reproducibility of multiple image sensors may be improved.

Furthermore, if a trench for a deep trench isolation portion is formedby one etching process, the depth of the trench may be very deep. Thus,the width of an upper portion of the trench may be substantially largeto prevent a not-open phenomenon of the trench. As a result, it may bedifficult to reduce the size of the deep trench isolation portion, e.g.,it may be difficult to form a highly integrated image sensor. However,since the deep trench isolation portion is formed using two etchingprocesses, the width of the deep trench isolation portion may berelatively reduced. As a result, it is possible to easily realize ahighly integrated image sensor.

The aforementioned embodiments may be combined in various combinationsto form additional embodiments.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of skill in the art as of thefiling of the present application, features, characteristics, and/orelements described in connection with a particular embodiment may beused singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwiseindicated. Accordingly, it will be understood by those of skill in theart that various changes in form and details may be made withoutdeparting from the spirit and scope of the present invention as setforth in the following claims.

1. An image sensor, comprising: a substrate including a first surface, asecond surface opposing the first surface, and a plurality of unit pixelregions; a shallow trench isolation layer adjacent to the first surface;a first deep trench isolation layer adjacent to the shallow trenchisolation layer and extending toward the second surface in thesubstrate; and a second deep trench isolation layer adjacent to thesecond surface and vertically overlapping the first deep trenchisolation layer, wherein the first and second deep trench isolationlayers isolate the unit pixel regions from each other.
 2. The imagesensor as claimed in claim 1, wherein the first deep trench isolationlayer is in contact with the second deep trench isolation layer.
 3. Theimage sensor as claimed in claim 1, wherein the first deep trenchisolation layer includes: a filling insulation layer; and a poly-siliconpattern in the filling insulation layer.
 4. (canceled)
 5. The imagesensor as claimed in claim 1, further comprising: a dopant injectionregion in the substrate and along sidewalls of the first and second deeptrench isolation layers.
 6. The image sensor as claimed in claim 1,wherein the second deep trench isolation layer includes: a fixed chargelayer; and a filling insulation layer in the fixed charge layer. 7.(canceled)
 8. The image sensor as claimed in claim 6, wherein the fixedcharge layer overlaps the second surface.
 9. (canceled)
 10. The imagesensor as claimed in claim 1, wherein a sidewall of the second deeptrench isolation layer is horizontally spaced apart from a sidewall ofthe first deep trench isolation layer.
 11. The image sensor as claimedin claim 1, wherein the first deep trench isolation layer is verticallyspaced apart from the second deep trench isolation layer, and the imagesensor includes a channel stop region between the first deep trenchisolation layer and the second deep trench isolation layer.
 12. Theimage sensor as claimed in claim 1, wherein at least one of the first orsecond deep trench isolation layers includes an air gap region. 13.(canceled)
 14. The image sensor as claimed in claim 1, wherein the firstand second deep trench isolation layers surrounds each of the unit pixelregions when viewed from a plan view.
 15. The image sensor as claimed inclaim 1, wherein a width of the first deep trench isolation layer isdifferent from a width of the second deep trench isolation layer. 16.The image sensor as claimed in claim 1, wherein a vertical length of thefirst deep trench isolation layer is different from a vertical length ofthe second deep trench isolation layer. 17-21. (canceled)
 22. An imagesensor, comprising: a substrate including a first surface, a secondsurface opposing the first surface, and a plurality of unit pixelregions; a first deep trench isolation layer adjacent to the firstsurface; and extending toward the second surface in the substrate; and asecond deep trench isolation layer adjacent to the second surface,wherein the second deep trench isolation layer overlaps the first deeptrench isolation layer when viewed from a plan view and wherein thefirst and second deep trench isolation layers isolate the unit pixelregions from each other.
 23. The image sensor as claimed in claim 22,wherein the first deep trench isolation layer has substantially aT-shaped cross section. 24-30. (canceled)
 31. An image sensor,comprising: a first pixel region; a second pixel region; a fixed chargelayer over the first and second pixel regions; a first isolation layerbetween the first and second pixel regions; and a second isolation layerbetween the first and second pixel regions, wherein the second isolationlayer overlaps the first isolation layer and wherein the first andsecond isolation layers isolate the first pixel region from the secondpixel region.
 32. The image sensor as claimed in claim 31, wherein thefixed charge layer includes a material to induce accumulation of holesadjacent a surface of each of the first and second pixel regions. 33.(canceled)
 34. The image sensor as claimed in claim 31, furthercomprising: a poly-silicon pattern in the second isolation layer,wherein the poly-silicon pattern has a first thermal expansioncoefficient, the first and second pixel regions are in or on a layerhaving a second thermal expansion coefficient, and the first thermalexpansion coefficient is substantially equal to the second thermalexpansion coefficient.
 35. The image sensor as claimed in claim 31,wherein the second isolation layer includes at least one of an oxygenpermeation preventing layer or a filling insulation layer.
 36. The imagesensor as claimed in claim 31, wherein the second isolation layerincludes: a first layer; and a second layer on the first layer, whereinthe first layer is closer to the first isolation layer than the secondlayer, and wherein the second layer is closer to a surface to receiveincident light than the first layer.
 37. The image sensor as claimed inclaim 36, wherein: the first layer includes one or more materials, andthe second layer includes one or more materials different from the oneor more materials of the first layer.